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Q&As
Is it worth retrofitting underfloor heating?
I’ve recently bought a 1960s bungalow that’s in need of renovation. I’m interested in getting underfloor heating in the bathroom, but do you think this is worth the expense in our case? The bathroom floor is concrete, and we also found out from a survey that it isn’t level. Given the age of the house, would we also need to address insulation and airtightness in the rest of the property? All the windows are already triple glazed.
One Answer
If it’s a 1960s bungalow, I am presuming that the concrete floors are not insulated. In that case, the heat you put into the floors will go in both directions, and the heat travelling downwards will be largely wasted. However, the bathroom is likely to be a very small percentage of the floor area, so this heat loss won’t be massive.
Any form of underfloor heating will raise the finished floor level (FFL). This is unless you remove that section of floor, re-lay it if necessary at lower level and reconstruct with insulation and the heating built in – but that’s going to be a really expensive and disruptive job, and won’t actually save much energy compared to the embodied energy of doing the job, so it’s hard to justify in environmental terms.
All that said, remember that a little insulation goes a long way, and it takes a lot more insulation to do only a little more work. So, if you can get 25mm of a high performance insulation in, for example, then it may be feasible to switch to underfloor heating. There are very good low profile wet systems around so the total increase in floor height could be less than 50mm. If you have plenty of head room in your bungalow, then this could be done, but might require alterations at doorways to raise lintels to preserve head height.
Lastly, wet systems are always to be preferred to electrical resistance systems, as electricity costs three times the price of gas or oil for each kWh of heat delivered. However, if you’re only looking at very occasional use in a very small space, then you might decide to hang the cost and go for an electrical underfloor system in the bathroom. But, don’t leave it on all day, since much of that very expensive heat will be going to waste.
And yes, do insulate the rest of the property! It’ll be cavity wall so you could fill this, or go for EWI, which would be a better job.
Nigel (sustainability expert)